. >> this k-9 responded to the newtown connecticut shooting. another dog working in law enforcement is holland. fox files met up with him and his handler, metropolitan transportation authority police officer doug joseph. this k-9 unit is helping to lead the fight against terrorism in the big apple. >> in the mta, what would he be sniffing for 12346789. >> here our primary concern is explosives on the transit system in the metro area. >> tell me how important dogs have become in the last several years to american security? >> what the dog lets us do is move around any place, any time. they are versatile and we are lucky to have them. >> in 2010 after the pentagon spent four years and $17,000 researching ied detection they announced that nothing is better than a dog. >> having a dog on point is very important and they have saved many lives. >> coming up, the unbreakababab >>> here at lackland air force base in texas, dogs aren't the only ones receiving training. so are military working dog handlers. >> i wanted to keep things, the longer you are